In 2009 Craig Gentry of IBM published a cryptographic proof that was that rare thing: a true breakthrough. He showed that it was possible to add and multiply encrypted data to produce a result that--when decrypted--reveals the result of performing the same operations on the original, unencrypted data. It's like being able to answer a question without knowing what the question is.

Called "fully homomorphic encryption," it has been dubbed the holy grail of cryptography.